bad size calculation for wrapping nodes (text or flex_wrap: Wrap)

[robtfm]

Bevy version

0.15.0-rc.3

What you did

render a bit of text with the following code.

use bevy::prelude::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

fn setup(mut commands: Commands) {
    commands.spawn(Camera3d::default());

    commands.spawn(Node::default()).with_children(|c| {
        c.spawn((Node {
            flex_direction: FlexDirection::Column,
            width: Val::Px(500.0),
            ..Default::default()
        },))
            .with_children(|c| {
                c.spawn((
                    Node {
                        min_width: Val::Px(500.0), // changing this to 499.999 works as expected
                        ..Default::default()
                    },
                    BackgroundColor::from(Color::srgba(0.0, 0.0, 1.0, 1.0)),
                ))
                .with_children(|c| {
                    c.spawn((Text::new("Some text and some more text"), ZIndex(1)));
                });
            });
    });
}

What went wrong

the text container is much too large vertically.

Additional info

• changing the min_width of the 3rd node to 499.999 or smaller sizes the text correctly (so maybe a propagation problem in taffy)
• making the text shorter makes the oversize decrease, making it longer makes it increase (so maybe a text measure problem)
• this was also an issue in 0.14.x

[robtfm]

definitely a taffy problem, we can get the same behaviour without text using a flex-wrap node with multiple children.

swapping c.spawn((Text::new("Some text and some more text"), ZIndex(1))); above with

                    c.spawn(Node {
                        flex_wrap: FlexWrap::Wrap,
                        ..Default::default()
                    })
                    .with_children(|c| {
                        for _ in 0..10 {
                            c.spawn((
                                Node {
                                    width: Val::Px(10.0),
                                    height: Val::Px(10.0),
                                    margin: UiRect::all(Val::Px(3.0)),
                                    ..Default::default()
                                },
                                BackgroundColor::from(Color::srgba(1.0, 0.0, 0.0, 1.0)),
                            ));
                        }
                    });

and with 499 min_width (this looks correct)

[robtfm]

and seems to still be an issue with taffy 0.6.1
@nicoburns - shall i open a taffy issue or this ^ enough?

[nicoburns]

Could you open an issue please?

[nicoburns]

@robtfm This should be fixed in Taffy 0.6.2